This invention relates to a dual-band output switching high-frequency transmission circuit and, more particularly, to a transmission mixer for use in a dual-band portable equipment to convert an intermediate frequency into a transmission frequency.
In prior art, in a portable telephone has been developed a dual-band portable equipment which uses two radio frequency bands such as 900 MHz and 1.8 GHz in the manner which are represented in GSM900/DCS-1800. As a transmission mixer for use in the dual-band portable equipment, a conventional miser is assigned with a band because the conventional mixer has only one output in the manner which will later be described in conjunction with FIG. 1.
In addition, various preceding arts related to the present invention are already known. By way of example, U.S. Pat. No. 4,916,411 or U.S. Pat. No. 4,916,411 discloses a variable frequency jitter generator which has a wide range of a bit rate without an unnecessary repetition of circuit elements. In U.S. Pat. No. 4,916,411, a circuit for generating jitter includes a mixer which mixes a jittered signal from a jitter generator with the output of a variable frequency oscillator to produce a broadband jittered output. A preferred form of the circuit uses a double frequency translation technique in which the output from a frequency oscillator is applied to a jitter generator and to a first frequency translation device to translate a variable input frequency to an intermediate frequency. The jittered signal and the intermediate frequency signal are then applied to a second frequency translation device to produce a jittered output at the variable input frequency.
In addition, Japanese Unexamined Patent Publication of Tokkai No. Hei 5-244,032 or JP-A 5-244032 describes xe2x80x9cDUAL-BAND RADIO COMMUNICATION APPARATUSxe2x80x9d to increase circuits which can be shared and reduce the size of the apparatus by converting an IF signal into a radio signal of a first or second band with common local oscillation signal consisting of an intermediate frequency of a transmission radio frequency. In JP-A 5-244032, for communication in the first or second band, a fundamental wave consisting of the intermediate frequency of a frequency synthesizer is outputted as a common local oscillation signal to a fixer. A first transmitting band pass filter circuit extracts the signal of the first band from the converted signal and sends it. A second transmitting band pass filter circuit extracts the signal of the second band from the converted signal and sends it. Then the received signals are inputted by an antenna selector to first and second receiving band pass filter circuits. The received signal is converted down by being multiplied by the local oscillation signal of a frequency synthesizer so that it is converted to a first reception IF frequency by a mixer. Thus, the circuits which can be shared are increased to reduce the size of the apparatus.
Furthermore, European Patent Publication No. 653851 or EP A 653851 discloses a radio communication apparatus of multi-band which is suitable to radio frequency bands which are relatively apart from each other. That is, the radio communication apparatus according to SP A 653851 comprises a common oscillator having an oscillation frequency which is selected so as to become about middle between a first frequency band and a second frequency band.
In addition, Japanese Unexamined Patent Publication of Tokkai No. Hei 8-223,073 or JP-A 8-233073 discloses a heterodyne xe2x80x9cDUAL BAND RADIO COMMUNICATION EQUIPMENTxe2x80x9d which is used in common in two bands like 800 MHz band and 1.5 GHz band in a digital land mobile radiotelephone. That is, in JP-A 8-223073, a reception intermediate frequency is made equal to a transmission/reception frequency difference between first and second radio frequency bands, and a frequency of a transmission intermediate frequency signal is set to two-fold frequency of the transmission/reception frequency difference. In addition, the dual band radio communication equipment comprises a first local oscillating circuit for oscillating a first local oscillation signal for converting a received signal of the first radio frequency band into a received intermediate frequency signal, a second local oscillating circuit for oscillating a second local oscillation signal for converting a received signal of the second radio frequency band into a received intermediate frequency signal, a first switch for performing switching between the first and the second local oscillation signals to produce a selected local oscillation signal which is supplied to a reception mixer, and a second switch for performing switching between the first or the second local oscillation signal and a third local oscillation signal The second switch produces an output signal which is supplied to a transmission mixer for multiplying the output signal by the transmission intermediate frequency signal to produce a transmission signal having a prescribed frequency band of the first radio frequency band and a transmission signal having a prescribed frequency band of the second radio frequency band.
Furthermore, Japanese Unexamined Patent Publication of Tokkai No. Hei 10-107,676 or JP-A 10-107676 discloses xe2x80x9cCOMMUNICATING APPARATUSxe2x80x9d which corresponds to a dual band in which the frequency intervals between a transmitting band and a receiving band are different from each other and also makes this apparatus small, light, inexpensive and which also is low power consumption by setting the frequency of a voltage-controlled offset signal oscillator (offset VCO) so that it may be equal to the difference of intervals between transmitting band and receiving band. The communication apparatus disclosed in JP-A 10-107676 appropriately combines an offset VCO, a first high frequency VCO and a second high frequency VCO and generates a high frequency that is needed for transmission and receiving. The difference of the two transmitting band and receiving band is set to be equal. Thereby, a high frequency signal that is needed for the transmission and receiving of the dual band can be created with minimum block structure. In addition, the frequency of an IF signal becomes equal in either case of two receiving bands, the structure of a receiving system after a receiving mixer can be simplified, and it is possible to make this apparatus light and be low power consumption.
Any of the above-mentioned Publications merely discloses an one-output mixer.
In the manner which will later be described in conjunction with FIGS. 2 and 3, a conventional dual-band output switching high-frequency transmission circuit is disadvantageous in that two transmission mixers becomes a necessity or an external switch for switching output frequency matching circuits or the like becomes a necessity extra.
It is therefore an object of this invention to provide a dual-band output switching high-frequency transmission circuit in which a switch for switching matching circuits is not necessitated.
It is another object of this invention to provide a transmission mixer for use in the above-mentioned dual-band output switching high-frequency transmission circuit.
It is still another object of this invention to provide a dual-band output switching high-frequency transmission circuit of the type described, which is capable of miniaturizing a circuit.
It is yet another object of this invention to provide a transmission mixer for use in the above-mentioned dual-band output switching high-frequency transmission circuit.
It is a further object of this invention to provide a dual-band output switching high-frequency transmission circuit of the type described, which is capable of reducing a consumed current.
It is a still further object of this invention to provide a transmission mixer for use in the above-mentioned dual-band output switching high-frequency transmission circuit.
Other objects of this invention will become clear as the description proceeds.
In order to achieve the above-mentioned objects, this invention adopts technical structure as follows. That is, this invention provides a circuit combining a following five items in order to simplify structure:
{circle around (1)} A mixer having two output ports;
{circle around (2)} A mixer having two output frequencies which are apart from each other;
{circle around (3)} A mixer having an output stage which may be connected to a two-band band pass filter;
{circle around (4)} A switching of two-band outputs can be carried out by switching a local frequency of a mixer; and
{circle around (5)} It is possible to decrease the number of a transmission mixer in a dual-band portable equipment to one.
On describing the gist of an aspect of this invention, it is possible to be understood that a transmission mixer is for use in a dual-band portable equipment to convert an intermediate frequency into a transmission frequency. According to this invention, the above-understood transmission mixer has a local input port supplied with a local signal having a local frequency from a local oscillator, an intermediate input port supplied with an input signal having an input frequency which is equal to the intermediate frequency, a first output port for producing a first output signal having a first output frequency, and a second output port for producing a second output signal having a second output frequency which is different from the first output frequency.
In the above-mentioned transmission mixer, it may be preferable that the first and the second output ports are connected to first and second loads, respectively, the first load is that where impedance-matching is made at the first output frequency, and the second load is that where impedance-matching is made at the second output frequency. In addition, the above-mentioned transmission mixer desirably may have a power-supply terminal applied with a power-supply voltage and a ground terminal having a ground potential and the transmission mixer may comprise a first npn-type bipolar transistor having a base electrode connected to the local input terminal, a collector electrode connected to the power-supply terminal through the first load, and an emitter electrode connected to a common node, a second npn-type bipolar transistor having a collector electrode connected to the power-supply terminal through the load and an emitter electrode connected to the common node, a third npn-type bipolar transistor having a collector electrode connected to the common node and an emitter electrode connected to the ground terminal, a first output capacitor connected between the collector terminal of the first npn-type bipolar transistor and the first output port, a second output capacitor connected between the collector terminal of the second npn-type bipolar transistor and the second output port, a capacitor connected between a base electrode of the second npn-type bipolar transistor and the ground terminal, and an input capacitor connected between a base electrode of the third npn-type bipolar transistor and the intermediate input terminal. In addition, the base terminals of said first through said third npn-type bipolar transistors are supplied with a bias voltage from a bias circuit.
On describing the gist of another aspect of this invention, it is possible to be understood that a dual-band output switching high-frequency transmission circuit is for use in a dual-band portable equipment. According to this invention, the above-understood dual-band output switching high-frequency transmission circuit comprises a first local oscillator for oscillating a first local signal having a first local frequency, a second local oscillator for oscillating a second local signal having a second local frequency which is different from the first local frequency, a transmission mixer having a local input port selectively supplied with one of the first and the second local signals, an intermediate input port supplied with an input signal having an input frequency of an intermediate frequency, and first and second output ports for producing first and second output signals having first and second output frequencies which are different from each other, a first band pass filter connected to the first output port and having a pass band of the first output frequency, and a second band pass filter connected to the second output port and having a pass band of the second output frequency.
In the above-mentioned dual-band output switching high-frequency transmission circuit, the first and the second local frequencies may be lower than the first and the second output frequencies, respectively, the first output frequency may be equal to that obtained by adding the input frequency to the first local frequency, and the second output frequency may be equal to that obtained by adding the input frequency to the second local frequency. In addition, the first and the second local frequencies may be higher than the first and the second output frequencies, respectively, the first output frequency maybe equal to that obtained by subtracting the input frequency from the first local frequency, and the second output frequency may be equal to that obtained by subtracting the input frequency from the second local frequency. Further, the first local frequency may be higher than the first output frequency, the second local frequency may be lower than said second output frequency, the first output frequency may be equal to that obtained by subtracting the input frequency from the first local frequency, and the second output frequency may be equal to that obtained by adding the input frequency to the second local frequency. Furthermore, the first local frequency may be lower than the first output frequency, the second local frequency may be higher than the second output frequency, the first output frequency may be equal to that obtained by adding the input frequency to the first local frequency, and the second output frequency may be equal to that obtained by subtracting the input frequency from the second local frequency.